Each known vehicle seat device, which has been disclosed in JP2000-211410A and JP2003-54343A, has a particular mechanism by which a headrest of a vehicle seat provided at a vehicle (hereinafter referred to as a first vehicle) is moved in the event of a vehicle collision in a front direction of the first vehicle in order to protect a passenger's head from an impact applied to the first vehicle from the rear thereof by such as a following vehicle (hereinafter referred to as a second vehicle).
Generally, when the passenger doesn't sit back on the vehicle seat with leaning his/her upper body backward against the seat back of the vehicle seat, and an impact is applied to the first vehicle from the rear thereof, the upper body of the passenger rapidly moves toward the seat back.
Specifically, the passenger's head rapidly moves backward toward the position of the headrest, and when the passenger's head contacts the headrest, the movement of the passenger's head in a rear direction is regulated. Then, the upper body of the passenger moves forward intensely. At this point, a load is applied to the passenger' neck, as a result, the passenger may suffer from a whiplash injury. According to the known vehicle seat device, the headset of the vehicle seat is moved forward relative to the seat back in order to shorten the distance of the movement of the passenger's head in a rear direction. In this configuration, the level of the load applied to the passenger's neck is reduced, as a result, chances that the passenger suffers from a whiplash injury can be reduced.
In this configuration, when the headrest is moved in a front direction when an impact is applied to the first vehicle from the rear thereof, the headrest needs to be accurately moved in a front direction in order to reduce the load applied to the passenger's neck so as to prevent the passenger from being whiplash injury.
However, it might happen that, for example, the headrest is actuated to move in a front direction even when an impact is not applied to the first vehicle and there is no need to protect the passenger's head from the impact. Specifically, in case that the vehicle seat device has a mechanism moving the headrest on the basis of a level of the load applied to the vehicle seat, the headrest might be moved when the vehicle seat device mistakenly determines the load applied by the passenger who seats on the vehicle seat as an impact applied by the following vehicle.
Further, even when there is no passenger in the vehicle, a headrest may be activated for a variety of reasons. In such case, when the headrest is configured to be retracted automatically by use of a drive generated at a motor or the like after it is moved in a front direction, the user won't even know whether or not the headrest is activated after the headset is restored to its original position. In other words, when the headrest is not appropriately activated, because the headrest becomes in a same state as that of the headrest restored to its original position, it is difficult to figure out whether or not the headrest is actuated correctly.
Further, even when an impact is applied to the first vehicle, the headrest may not be actuated when, for example, the level of the actual impact strength that is applied to the first vehicle is smaller than the level of the impact strength that is set as a required level to actuate the headrest.
The user has not been able to recognize what is a factor of the improper actuation of the headrest. Thus, a need exists to provide a vehicle seat device that can improve the actuating performance of the headrest.